Heat exchanger and heat exchange device

ABSTRACT

A heat exchanger including a tubular core case, a pair of end plates for closing opposite ends of the core case, and a plurality of heat exchange tubes supported at opposite ends thereof by the end plates and allowing flow of a first heating medium inside thereof. One end plate is disposed on an upstream side of the first heating medium as an upstream end plate while the other end plates is disposed on a downstream side of the first heating medium as a downstream end plate. The downstream end plate comprises a downstream bottom surface part for supporting downstream end parts of the heat exchange tubes, and a downstream wall part formed integrally with and rising from a peripheral edge of the downstream bottom surface part, and a top end part of the downstream wall part is oriented toward upstream of the flow of the first heating medium.

FILED OF THE INVENTION

The present invention relates to a heat exchanger and a heat exchange device employing the heat exchanger.

BACKGROUND OF THE INVENTION

Generally, a heat exchanger is designed to effect heat exchange between a first heating medium that flows along an inner periphery of a heat exchange tube and a second heating medium that flows along an outer periphery of the heat exchange tube. It is known to employ a heat exchanger in a heat exchange device (see JP 2012-184681 A, for example).

Referring to FIG. 13 hereof, explanation will be made as to the heat exchange device disclosed in JP 2012-184681. As shown in FIG. 13, an exhaust heat recovery apparatus 200, known also as a heat exchange device, includes a heat recovery passage 202 in which a heat exchanger 201 is housed for effecting heat exchange, and a bypass 203 branched off from the heat recovery passage 202 and where heat exchange is not performed.

The heat exchanger 201 is comprised of a core case 211, a pair of end plates 212, 213 for closing respective ends of the core case 211, and a plurality of heat exchange tubes 215 disposed between the two end plates 212, 213 and allowing an exhaust gas to flow inside thereof. Heat exchange is effected between the exhaust gas that flows through the heat exchange tubes and a medium that flows externally.

The exhaust heat recovery apparatus 200 employing the heat exchanger 210 is generally mounted to an underside of a floor of a vehicle body. Since a mounting space on the underside of the vehicle body floor is small, it is desired that the exhaust heat recovery apparatus 200 be compact and small. If the heat exchanger 210 is downsized, the exhaust heat recovery apparatus per se becomes compact and small.

In addition, in a case in which the heat exchanger 210 is employed in an apparatus other than the exhaust heat recovery apparatus 200, if the heat exchanger 210 is downsized, this brings the advantage that the apparatus in which the heat exchanger 210 is employed can be positioned with increased freedom. There is therefore a demand for downsizing of a heat exchanger.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a heat exchanger comprising: a tubular core case; a pair of end plates for closing opposite ends of the core case; and a plurality of heat exchange tubes supported at opposite ends by the end plates and allowing a first heating medium to flow inside thereof, so as to effectuate heat exchange between the first heating medium and a second heating medium flowing along an outer periphery of the heat exchange tubes, wherein one of the end plates is disposed on an upstream side of flow of the first heating medium as an upstream end plate while another one of the end plates is disposed on a downstream side of the flow of the first heating medium as a downstream end plate, the downstream end plate comprises a downstream bottom surface part for supporting downstream end parts of the heat exchange tubes, and a downstream wall part formed integrally with and rising from a peripheral edge of the downstream bottom surface part, and a top end part of the downstream wall part is oriented toward upstream of the flow of the first heating medium.

In the above-described inventive arrangement, the downstream end plate is comprised of the downstream bottom surface part for supporting the heat exchange tubes, and the downstream wall part formed integrally with and rising from the peripheral edge of the downstream bottom surface part, and the top end part of the downstream wall part is disposed in orientation toward an upstream side. Since the top end part of the downstream wall part is oriented toward upstream, the top end part of the downstream wall part is positioned further upstream than the downstream end parts of the heat exchange tubes, whereby the heat exchanger is downsized.

Preferably, the downstream wall part is joined with the core case only at a top end side thereof.

It is preferred that the upstream end plate comprise an upstream bottom surface part for supporting upstream end parts of the heat exchange tubes, and an upstream wall part formed integrally with and rising from a peripheral edge of the upstream bottom surface part, and the top end part be oriented toward downstream of the flow of the first heating medium.

Desirably, the upstream wall part is joined with the core case only at a top end side thereof.

It is preferred that the core case have a second heating medium inlet for introducing the second heating medium into the core case, and a guide part be provided in the vicinity of the second heating medium inlet for guiding the second heating medium toward the upstream side of the heat exchange tubes.

In a preferred form, the guide part comprises a sheet-shaped guide plate joined with an inner peripheral surface part of the core case and forming a closed cross section between the guide plate and the inner peripheral surface part of the core case, while the guide plate has a guide aperture formed at an upstream-side end part thereof, through which aperture the second heating medium is guided toward the upstream side of the heat exchange tubes.

It is preferred that the guide part comprise a sheet-shaped guide plate joined with an outer peripheral surface part of the core case and defining a closed cross section between the guide plate and the outer peripheral surface part of the core case, and the core case have a guide aperture formed at an upstream end part thereof, through which aperture the second heating medium is guided toward the upstream side of the heat exchange tubes.

Desirably, the guide aperture is formed at a position corresponding to an inter-layer space of the heat exchange tubes.

In a desired form, the core case has a recessed part recessed inwardly along a direction of flow of the first heating medium.

According to a second aspect of the present invention, there is provided a heat exchange device which comprises: a branching part for allowing passage of an exhaust gas therethrough and branching the exhaust gas into two streams; a first flow passage extending from the branching part; a second flow passage extending from the branching part along the first flow passage; a heat exchanger disposed on the second flow passage for recovering energy from heat of the exhaust gas; and a valve disposed openably/closably on one of the first flow passage and the second flow passage for changing a direction of flow of the exhaust gas, wherein the heat exchanger comprises a heat exchanger according to the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a top plan view illustrating an exhaust heat recovery apparatus employing a heat exchanger according to a first embodiment of the present invention:

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a perspective view illustrating the heat exchanger of FIG. 2;

FIG. 4 is an exploded perspective view illustrating a lower case half and a guide plate;

FIG. 5 is a perspective view illustrating the lower case half and the guide plate joined together;

FIG. 6 is a schematic view illustrating an operation of the heat exchanger of FIG. 2;

FIG. 7 is a cross-sectional view illustrating a heat exchanger according to a second embodiment of the present invention;

FIG. 8 is a perspective view illustrating the heat exchanger of FIG. 7;

FIG. 9 is a cross-sectional view taken along line 9-9 of FIG. 7;

FIG. 10 is an exploded perspective view illustrating a lower case half and a guide plate according to the second embodiment of the present invention;

FIG. 11 is a perspective view illustrating the lower case half and the guide plate, joined together, of FIG. 10;

FIG. 12 is a cross-sectional view illustrating a heat exchanger according to a third embodiment of the present invention; and

FIG. 13 is a cross-sectional view illustrating a conventional, basic arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

Reference is made initially to FIG. 1. As shown in FIG. 1, an exhaust heat recovery apparatus 10 (heat exchange device) includes an exhaust gas inlet 11 for introducing exhaust gas (first heating medium) generated in an internal combustion engine (not shown), a branching part 12 connected to the inlet 11, a first flow passage 13 connected to the branching part 12 and extending downstream of the inlet 11, a second flow passage 14 extending from the branching part 12 along the first flow passage 13, a heat exchanger 30 forming part of the second flow passage 14 for transmitting heat of the exhaust gas to a medium (second heating medium), a thermoactuator 16 connected to the heat exchanger 30, a valve chamber 17 to which the first and second flow passages 13, 14 are connected at downstream ends thereof, a discharge outlet 18 connected to the valve chamber 17 for discharging the exhaust gas, and a valve housed in the valve chamber 17 and adapted to close the first flow passage 13 or the second flow passages 14. The valve chamber 17 serves also as a merging part where streams of the exhaust gas passed through the first and second flow passages merge or meet.

In the state shown in the Figure, the valve 19 closes the first flow passage 13. At this time, the second flow passage 14 is opened to allow the exhaust gas to pass therethrough. On the other hand, when the valve 19 swings on a certain condition, the valve 19 closes the second flow passage 14, whereupon the first flow passage 13 is opened to allow passage of the exhaust gas therethrough.

A medium introducing pipe 21 (second heating medium introducing pipe) is connected to a side of the heat exchanger 30 for introducing heating medium. An actuator support member 22 is connected to the heat exchanger 30 for supporting the thermoactuator 16. A medium discharge pipe 23 (second heating medium discharge pipe) is connected to the actuator support member 22 for discharging the heating medium.

Namely, the medium is introduced into the heat exchanger 30 through the medium introducing pipe 21. The thus-introduced medium receives heat from the exhausted gas within the heat exchanger 30 and discharged through the medium discharge pipe 23. That is, the heat exchanger 30 recovers energy of the exhaust gas. Detailed discussion as to the heat exchanger 30 will be made with reference to Figures that follow.

As shown in FIG. 2, the heat exchanger 30 is comprised of a generally square-tube-shaped core case 31 adapted to allow flow of the medium internally, upstream and downstream end plates 32, 33 mounted so as to close openings at opposite ends of the core case 31, a heat exchange tube 34 mounted between the upstream and downstream end plates 32, 33 and adapted to allow passage of the exhaust gas internally, and a fin 35 housed in the heat exchange tube 34.

Turning now to FIG. 3, the upstream end plate 32 includes a plurality of heat exchange tubes 34 inserted thereinto. The downstream end plate 33 is similarly configured.

The core case 31 is comprised of a lower case half 41 having a generally U-shape as viewed in front elevation and forming a lower half of the core case 31, and an upper case half joined with the lower case half 41 to form an upper part of the core case 31. The upper case half 42 is also generally U shaped as view in front elevation.

The lower case half 41 has a side surface portion 41 a which is provided with a medium inlet 41 b (second heating medium inlet) for introducing medium. The medium introducing pipe 21 (FIG. 1) is connected to the medium inlet 41 b.

The upper case half 42 is comprised of a connecting part 42 a connected to the upstream end plate 32, the downstream end plate 33 and the lower case half 41, and a recessed part 42 b recessed inwardly from the connecting part 42 a. On an upper surface part 42 c of the recessed part 42 b, a medium discharge outlet 42 d (second heating medium discharge outlet) is provided for discharging the medium. The actuator support member 22 is connected to the medium discharge outlet 42 d.

Turning back to FIG. 2, the upstream end plate 32 includes a generally rectangular-shaped upstream bottom surface part 32 a for supporting an upstream end part 34 a of the heat exchange tube 34, and an upstream wall part 32 b formed integrally with and rising from a peripheral edge of the upstream bottom surface part 32 a. The upstream wall part 32 b extends toward downstream from the upstream bottom surface part 32 a. Top end part 32 c of the upstream wall part 32 b is located at a downstream-most position.

The upstream bottom surface part 32 a has a plurality of support holes 32 d for allowing passage of and supporting the heat exchange tube 34. Of the upstream wall part 32 b, only the top end 32 c is joined with the core case 31.

The downstream end plate 33 is configured similarly. Namely, the downstream end plate 33 is comprised of a downstream bottom surface part 33 a having a generally rectangular shape and supporting a downstream end part 34 b of the heat exchange tube 34, and a downstream wall part 33 b formed integrally with and rising from a peripheral edge of the downstream bottom surface part 33 a. The downstream wall part 33 b extends from the downstream bottom surface part 33 a toward upstream. Top end part 33 c of the downstream wall part 33 b is located at an upstream-most position.

The downstream bottom surface part 33 a has a plurality of support holes 33 d for allowing passage of and supporting the heat exchange tube 34. Of the downstream wall part 33 b, only the top end part 33 c is connected to the core case 31.

The core case 31 has a recessed part 42 b recessed inwardly along the direction of flow of the exhaust gas. Provision of the recessed part 42 b imparts increased rigidity to the core case 31. This makes it possible to increase rigidity against the direction of expansion of the medium and hence to impart a prolonged life to the heat exchanger 10.

Of the upstream wall part 32 b, only the top end part 32 c is connected to the core case 31. Thus, the peripheral edge of the upstream wall part 32 b is not joined with the core case 31. As a result, a member for introducing exhaust gas can be connected directly to the peripheral edge of the upstream wall part 32 b. Since direct connection of the heat exchanger 10 with the associated flow passage becomes possible, an additional part for connecting the heat exchange with the associated flow passage will not be required. This leads to the advantage that the number of required parts may be decreased. The same can be said of the downstream end plate 33.

At a lower part of the core case 31, there is provided a guide part 37 for guiding the medium toward upstream of the heat exchange tube 34. The guide part 37 is comprised of a guide plate 50 which is connected to an inner peripheral surface part 31 a of the core case 31 in such a manner as to form a closed cross section between the guide plate 50 and the inner peripheral surface part 31 a.

The upstream wall part 32 b of the upstream end plate 32 and the downstream wall part 33 b of the downstream end plate 33 desirably have a length in the range of 10 mm to 24 mm. The upstream and downstream wall parts 32 b, 33 b are overlapped with respective upstream and downstream parts in an overlap range of 2 mm to 7 mm. Ranges left between the overlap ranges are 6 mm to 10 mm. The portions between the overlap ranges are set to have a length that will not allow them to overlap with their respective weld beads.

As shown in FIG. 4, the guide plate 50 is obtained by press-forming a steel sheet into a generally L shape. More specifically, the guide plate 50 is comprised of an introducing part 51 provided at a position corresponding to the medium inlet 41 b so as to cover the medium inlet 41 b, a guide-forming part 52 extending from a lower end of the introducing part 51 laterally of the core case 31, and a flange part 53 integrally provided at a peripheral edge of the introducing inlet 51 and the guide-forming part 52 and adapted to be joined with the inner peripheral surface part 31 a of the core case 31.

The introducing part 51 bulging from the flange part 53 defines, jointly with the guide-forming part 52, a closed cross-section between the inner peripheral surface part 31 a and the guide-forming part 52. At an upstream end part, the guide-forming part 52 has a plurality of guide apertures 52 a, 52 a for guiding the medium toward upstream of the heat exchange tube 34 (FIG. 2).

In the state in which the guide plate 50 is attached to the lower case half 41, as shown in FIG. 5, the medium introduced through the medium inlet 41 b, as shown by arrow (1), is guided into the inside of the core case 31 by the guide-forming part 52. The medium thus guided into the core case 31 is caused to flow through the guide apertures 52 a, 52 a toward upstream of the core case 31, as shown by arrows (2), (2).

Turning back to FIG. 2, the introduced medium flows first through the core case 31 toward upstream. Flowing through the upstream is the exhaust gas that is yet to be heat-exchanged. Efficient heat exchange is enabled by effectuating heat exchange between a non-heat-exchanged, high-temperature exhaust gas and a non-heat-exchanged, low-temperature medium.

By causing the medium to flow upstream, it becomes possible to suppress an increase in stress that arises by excessive heating of the upstream end plate 32. This makes it possible to reduce a load applied to the heat exchanger 30 and hence to prolong the life of the heat exchanger 30. The medium may boil by heating it to a high temperature. By making the medium flow upstream, it becomes possible to stably supply the medium upstream and hence to avoid boiling of the medium. As a result, improved heat exchange efficiency is provided.

Note also that the guide part is formed of the guide plate 50 of sheet shape that defines a closed cross section between the plate 50 and the core case 31 and that the upstream end part of the guide plate 50 is provided with the guide apertures 52 a. By this simple arrangement, it becomes possible to make the medium flow upstream of the heat exchange tube 34.

As shown in (a) of FIG. 6, a heat exchanger 230, a known example for comparison, includes an upstream end plate 232 with an upstream wall part 232 b extending from an upstream bottom surface part 232 a toward upstream. A downstream end plate 233 includes a downstream wall part 233 b extending from a downstream bottom surface part 233 a toward downstream.

When the upstream wall part 232 b is oriented toward upstream (leftward), a top end part 232 c of the upstream wall part 232 b projects forward from the upstream end part 34 a of the heat exchange tube 34 thereby increasing the overall length of the heat exchanger 230.

The same discussion is applicable to the downstream end plate 233.

Namely, when the downstream wall part 233 b is oriented toward downstream, a top end part 233 c of the downstream wall part 233 b projects rearward from the downstream end part 34 b of the heat exchange tube 34 thereby increasing the overall length of the heat exchanger 230.

Reference is now made to FIG. 6( b) illustrating the heat exchanger 30 according to the inventive embodiment. As shown in the Figure, the upstream end plate 32 is comprised of the upstream bottom surface part 32 a supporting the heat exchange tube 34, and the upstream wall part 34 a formed integrally with and rising from the peripheral edge of the upstream bottom surface part 32 a. The top end part 32 c of the upstream wall part 32 b is connected to the core case 31.

Since the top end part 32 c of the upstream wall part 32 b is oriented toward downstream, the top end part 32 c of the upstream wall part 32 b is positioned nearer to downstream than the upstream end part 34 a of the heat exchange tube 34. As a result, the overall length of the heat exchanger 30 becomes smaller (see α), whereby the heat exchanger 30 is downsized.

Note also that the top end part 32 c of the upstream wall part 32 b extends rearward from the upstream end part 34 a of the heat exchange tube 34 and is connected to the core case 31. As a result, the core case 31 is made shorter by the length of the upstream wall part 32 b and hence downsized.

In the arrangement explained above, it is possible to make the medium flow through an area enclosed by the upstream wall part 32 b and the upstream bottom surface part 32 a. The core case 31 is downsized an amount equivalent to the area and hence the heat exchanger 30 per se is downsized.

The same discussion is applied to the downstream end plate 33. Since the top end part 33 c of the downstream wall part 33 b is oriented toward upstream, the top end part 33 c of the downstream wall part 33 b is positioned nearer to upstream than the downstream end part 34 b of the heat exchange tube 34. As a result, the overall length of the heat exchanger 30 is decreased (see β) to thereby downsize the heat exchanger 30.

Note additionally that the top end part 33 c of the downstream wall part 33 b extends forward from the downstream end part 34 b of the heat exchange tube 34 and is joined with the core case 31. The core case 31 is decreased in length by the length of the downstream wall part 33 b, whereby the core case 31 is downsized.

Note further that in the arrangement explained above, it is possible to make the medium flow through an area enclosed by the downstream wall part 33 b and the downstream bottom surface part 33 a. This makes it possible to downsize the core case 31 by the amount equivalent to the area and hence the heat exchanger 30 as a whole.

As compared with the known example heat exchanger 230 (FIG. 6( a)), the upstream side of the inventive heat exchanger 30 became shorter by α. The same discussion is applicable to the downstream end plate 33. Compared to the know example heat exchanger 230, the inventive core case 30 became shorter in the downstream side by β. To sum up, the heat exchanger 30 of the inventive embodiment is made shorter by α+β.

Referring also to FIG. 1, it will readily be appreciated that by employing the heat exchanger 30 rendered compact as explained above, the exhaust heat recovery apparatus 10 per se is made compact. It is desirable that freedom of positioning of the exhaust heat recovery apparatus 10 be increased.

Embodiment 2

Discussion will be made next as to a second embodiment of the present invention with reference to FIGS. 6-11.

FIG. 7 illustrates in cross-section a heat exchanger according to a second embodiment of the present invention in correspondence with FIG. 2. The heat exchanger according to the second embodiment differs from the heat exchanger shown in FIG. 2 in that the core case and the guide part are constructed differently.

As shown in FIGS. 7 and 8, the heat exchanger 60 has a core case 61 which is comprised of a lower case half 71 having a generally U shape as seen in front elevation, an upper case half 72 having a generally U shape as seen in front elevation and coupled with the lower case half 71 from above, and a guide plate joined with a side surface and a bottom surface of the lower case half 71 from outside.

The lower case half 71 is comprised of joining parts 71 a, 71 a joined with the upstream end plate 32 and the downstream end plate 33, and a recessed part 71 b provided between the joining parts 71 a, 71 a and recessed inwardly. The recessed part 71 b is comprised of tapered parts 71 c, 71 c extending inclinedly from end parts of the joining parts 71 a, 71 a, and a planar part 71 d extending between the tapered parts 71 a, 71 c and parallel to the heat exchange tube 34.

The guide plate 80 is comprised of an inlet part 81 joined at a position corresponding to a side surface of the lower case half 71, a guide forming part 82 extending from a lower end of the inlet part 81 in a direction of width of the core case 61, and a flange part 83 formed integrally with peripheral edges of the inlet part 81 and the guide forming part 82 and joined with an outer peripheral surface part 61 b of the core case 61.

The inlet part 81 is provided with a medium inlet (second heating medium inlet) 81 a for introducing the heating medium. The medium introducing pipe 21 is connected to the medium inlet 81 a.

The inlet part 81 and the guide forming part 82 jointly define a closed cross section between them and an outer peripheral surface part 61 b of the core case 61 to thereby provide a guide part 67. The upstream tapered part 71 c is formed with a guide aperture 71 e for guiding the medium toward the upstream of the heat exchange tube 34. In addition, a plurality of small apertures 71 f, smaller than the guide aperture 71 e, is formed in the planar part 71 d.

As shown in FIG. 9, the guide aperture 71 e and the small apertures 71 f are formed at locations between corresponding layers of the heat exchange tube 34. It becomes possible to make the medium flow toward the interlayer space. By thus making the medium flow directly to locations where flow passage areas are large, the medium flows smoothly. As a result, heat exchange can be effected efficiently.

Referring now to FIG. 10, the recessed part 71 b is formed to run all around the lower case half 71. The guide part 67 is constructed by covering the thus-formed outer peripheral surface part 61 b of the lower case half 71 with the guide plate 80.

As can be appreciated from FIG. 11, the guide aperture 71 e has a size larger than those of the small apertures 71 f. Thus, the medium fed in through the medium inlet 81 a, as shown by arrow (5), flows on toward upstream chiefly through the guide aperture 71 e, as shown by arrow (6). On the other hand, a remaining portion of the medium is introduced into the core case 61 through the small apertures 71 f, as shown by arrow (7). The medium is introduce into the core case 61 through the guide aperture 71 e as a major stream and through the small apertures 71 f. As a result, it becomes possible for the medium to flow into the core case 61 in larger quantity, thereby enabling efficient heat exchange.

Embodiment 3

Explanation will be made next as to a third embodiment of the present invention with reference to FIG. 12 wherein the construction of a heat exchanger according to the third embodiment is shown in cross section in correspondence with the arrangement of FIG. 2.

As shown in FIG. 12, a heat exchanger 90 includes an upstream end plate 92 which is comprised of an end plate body 101 connected to the core case 31 and having a generally U shape as viewed in cross section, and a support plate 102 connected to the end plate body 101 and supporting the heat exchange tube 34.

The end plate body 101 is comprised of an upstream bottom surface part 101 a and an upstream wall part 101 b formed integrally with and rising from a peripheral edge of the upstream bottom surface part 101 a. A rectangular aperture 101 c is formed in the upstream bottom surface part 101 a. The support plate 102 is joined with the peripheral edge of the rectangular aperture 101 c. The support plate 102 has a thickness smaller than that of the end plate 101.

The same discussion is applied to the downstream end plate 93. The downstream end plate 93 is comprised of an end plate body 106 joined with core case 31 and having a generally U shape as viewed in cross section, and a support plate 107 connected to the end plate body 106 for supporting the heat exchange tube 34.

The end plate body 106 is comprised of a downstream bottom surface part 106 a and a downstream wall part 106 b formed integrally with and rising from the peripheral edge of the downstream bottom surface part 106 a. A rectangular aperture 106 c is formed in the downstream bottom surface part 106 a. A support plate 107 is connected to the peripheral edge of the rectangular aperture 106 c. The support plate 107 has a thickness smaller than that of the end plate body 106.

The upstream end plate 92 and the downstream end plate 93 are positioned differently in orientation. In the upstream end plate 92, the upstream wall part 101 b is extends from the upstream wall part 101 a toward upstream. As a result, a top end part 101 d of the upstream wall part 101 b extends in a direction away from the core case 31. On the other hand, in the downstream end plate 93, the downstream wall part 106 b extends from the downstream bottom surface part 106 a toward upstream. As a result, a top end part 106 d of the downstream wall part 106 b extends toward the core case 31.

Even when the top end part 106 d of the downstream wall part 106 b is oriented toward upstream while the top end part 101 d of the upstream wall part 101 b is not oriented toward downstream as above, advantageous effects aimed at by the present invention can be achieved. In other words, to an extent in which the top end part 106 d of the downstream wall part 106 b is oriented toward upstream, the core case 31 can be downsized (see β of FIG. 6). This further leads to downsizing of the heat exchanger 90.

Hot exhaust gas flows through the heat exchange tube 34 and the heat of the gas causes the tube 34 to stretch. Since the thickness of the support plate 102 is smaller than the thickness of the end plate body 101, the support plate 102 has smaller flexural rigidity than the end plate body 101. Thus, compared to the end plate body 101, the support plate 102 is liable to bend. Since the heat exchange tube 34 is inserted to a portion liable to bend, stretch of the heat exchange tube 34 can be absorbed by flexure or bend. This makes it possible to reduce a load applied to the heat exchange tube 34 and hence to prolong the life of the heat exchanger 90. The same goes to the downstream end plate 93.

It should also be appreciated that even when both the upstream end plate 92 and the downstream end plate 93 are oppositely oriented, the advantageous effects of the invention can be produced (see α of FIG. 6). Namely, it is possible that the top end part 101 d of the upstream end plate 92 be joined with the core case 31 while the top end part 106 d of the downstream end plate 93 be disposed to extend away from the core case 31 toward downstream.

Although the heat exchanger of the present invention has thus far been described as being applied to an exhaust heat recovery apparatus, it may readily be applied to an EGR (Exhaust Gas Recirculation) air conditioner, a cogeneration system and a thermoelectric generation system. It may also be applied to other systems than those as above in which heat exchange is carried out between an exhaust gas and a medium.

It can also be appreciated by a person skilled in the art that part of the heat exchange according to the third embodiment can be applied to the heat exchanger according to the first embodiment. Namely, the embodiments can be combined with one another as necessary.

Obviously, various minor changes are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described above. 

What is claimed is:
 1. A heat exchanger comprising: a tubular core case; a pair of end plates for closing opposite ends of the core case; and a plurality of heat exchange tubes supported at opposite ends by the end plates and allowing a first heating medium to flow inside thereof, so as to effectuate heat exchange between the first heating medium and a second heating medium flowing along an outer periphery of the heat exchange tubes, wherein one of the end plates is disposed on an upstream side of flow of the first heating medium as an upstream end plate while another one of the end plates is disposed on a downstream side of the flow of the first heating medium as a downstream end plate, the downstream end plate comprises a downstream bottom surface part for supporting downstream end parts of the heat exchange tubes, and a downstream wall part formed integrally with and rising from a peripheral edge of the downstream bottom surface part, and a top end part of the downstream wall part is oriented toward upstream of the flow of the first heating medium.
 2. The heat exchanger of claim 1, wherein the downstream wall part is joined with the core case only at a top end side thereof.
 3. The heat exchanger of claim 1, wherein the upstream end plate comprises an upstream bottom surface part for supporting upstream end parts of the heat exchange tubes, and an upstream wall part formed integrally with and rising from a peripheral edge of the upstream bottom surface part, and the top end part is oriented toward downstream of the flow of the first heating medium.
 4. The heat exchanger of claim 3, wherein the upstream wall part is joined with the core case only at a top end side thereof.
 5. The heat exchanger of claim 1, wherein the core case has a second heating medium inlet for introducing the second heating medium into the core case, and a guide part is provided in a vicinity of the second heating medium inlet for guiding the second heating medium toward the upstream side of the heat exchange tubes.
 6. The heat exchanger of claim 5, wherein the guide part comprises a sheet-shaped guide plate joined with an inner peripheral surface part of the core case and forming a closed cross section between the guide plate and the inner peripheral surface part of the core case, and the guide plate has a guide aperture formed at an upstream-side end part thereof, through which aperture the second heating medium is guided toward the upstream side of the heat exchange tubes.
 7. The heat exchanger of claim 5, wherein the guide part comprises a sheet-shaped guide plate joined with an outer peripheral surface part of the core case and defining a closed cross section between the guide plate and the outer peripheral surface part of the core case, and the core case has a guide aperture formed at an upstream end part thereof, through which aperture the second heating medium is guided toward the upstream side of the heat exchange tubes.
 8. The heat exchanger of claim 6, wherein the guide aperture is formed at a position corresponding to an inter-layer space of the heat exchange tubes.
 9. The heat exchanger of claim 1, wherein the core case has a recessed part recessed inwardly along a direction of flow of the first heating medium.
 10. A heat exchange device comprising: a branching part for allowing passage of an exhaust gas therethrough and branching the exhaust gas into two streams; a first flow passage extending from the branching part; a second flow passage extending from the branching part along the first flow passage; a heat exchanger disposed on the second flow passage for recovering energy from heat of the exhaust gas; and a valve disposed openably/closably on one of the first flow passage and the second flow passage for changing a direction of flow of the exhaust gas, wherein the heat exchanger comprises a heat exchanger defined in claim
 1. 